1. Field of the Invention
The present invention relates to an amplifying circuit, a semiconductor integrated circuit having the same mounted thereto, a wireless transmission system having the same mounted thereto, and a communication apparatus having the same mounted thereto. For example, the present invention relates to a high-frequency amplifying circuit which is applied to each of a communication apparatus on a transmission side and a communication apparatus on a reception side each of which operates in an Ultra Wide Band (UWB) or in a millimeter waveband.
2. Description of the Related Art
A broadband amplifying circuit which has flat amplification characteristics in a wide frequency range, for example, is proposed in Japanese Patent Laid-Open Nos. 2009-005137 and 2007-195189 (hereinafter referred to as Patent Documents 1 and 2) as an amplifying circuit which can respond to both requests for a broadband and a large gain.
For example, Patent Document 1 proposes a high-frequency circuit. This high-frequency circuit is configured as follows. That is to say, the high-frequency circuit includes a transistor, a load, a connection point, and a series circuit. In this case, the transistor has a source terminal a potential at which is fixed, and a gate terminal at which an input signal is received. The load is connected to a drain terminal of the transistor. The drain terminal of the transistor, and the load are connected to each other at the connection point. Also, in the series circuit, an inductor and a capacitor are connected in series with an output terminal of the high-frequency circuit. In addition, a band-pass filter having predetermined characteristics is composed of an output equivalent circuit expressing an output impedance of the transistor, the load, and the series circuit. In a word, a broadband amplifying circuit having a broadband of GHz or more is realized in the form of a load circuit using the inductor.
Patent Document 2 proposes a differential transimpedance amplifying circuit including a first operational amplifier, a second operational amplifier, a first feedback element, a second feedback element, a third feedback element, and a fourth feedback element. In this case, the first operational amplifier has a first inverting input terminal, a first non-inverting input terminal, a first inverting input terminal, and a first non-inverting output terminal. The second operational amplifier has a second inverting input terminal, a second non-inverting input terminal, a second inverting input terminal, and a second non-inverting output terminal. The second non-inverting output terminal is connected to the first inverting input terminal. The second non-inverting output terminal is connected to the first inverting input terminal. The first feedback element is connected to each of the first non-inverting input terminal and the first inverting input terminal. The second feedback element is connected to each of the first inverting input terminal and the first non-inverting input terminal. The third feedback element is connected to each of the second inverting input terminal and the first inverting output terminal. Also, the fourth feedback element is connected to each of the first non-inverting input terminal and the first non-inverting output terminal. In a word, a broadband amplifying circuit having a broadband of GHz or more is realized in the form of a resistance feedback type circuit.